Method installing a duct, device for carrying out said method, and a tape-shape element for use with said method

ABSTRACT

Method for installing a duct where an existing longitudinal member is present along a section over which the duct is to be installed. The longitudinal member is utilized as a guide for the duct. The tape-shaped element is closed around the longitudinal element through mating of complementary coupling devices longitudinally situated along the tape-shaped member so as to form a duct, with the coupled tape-shaped element then being propelled along the longitudinal element to extend the duct. The tape-shaped element can house an optical fiber cable. Through use of such a tape-shaped element, the duct, illustratively housing an optical fiber cable, can be formed around an existing (e.g. copper) telecommunications cable with any need to interrupt or remove that cable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for installing a duct, a longitudinalmember being present along the section over which the duct is to beinstalled, the present longitudinal element being made use of as aconductor for the duct to be installed, and the duct being propelled.

2. Description of the Prior Art

A method of installing a duct is known from U.S. Pat. No. 5,639,183. Theknown method is intended for installing—instead of an existingtelecommunication cable lying in the ground, particularly a coppercable—a duct through which an optical cable may be conducted. In theevent of said method, the existing cable is excavated at a suitablepoint, and cut through. The duct is slid over an end released in thismanner. To install the duct in the soil surrounding the existing cableover a greater length, a liquid—e.g., water—is conducted through theduct under pressure; it washes away the ground around the existingcable, while at the same time the duct is pushed forward. In thismanner, a duct, or a duct consisting of several coupled segments, may beinstalled underground over a great distance along an existing cable,without much excavation work being required for said purpose. Afterhaving been installed, the cable, if so desired, may be pulled out ofthe duct. One of the advantages of the known method is that curvysections are easy to follow, without expensive positioning equipment.

It should be noted that, in the present application, the word “duct”signifies any tubular member, without restriction as to its application,although in the application, more specifically, applying the inclusionof telecommunication cables is dealt with. In this connection, it is notimpossible that the duct has already been provided, in advance, with oneor more cables.

The known method is particularly suitable for replacing the existingcopper telecommunication cable with a cable duct in which an opticalfibre cable may be installed for installing, e.g., fibre up to the user,i.e. up to the home or company. The optical fibre may be installed inthe duct, e.g., by way of blowing or pulling, installing by way ofblowing being preferred, since in this case the forces exercised arespread out over the entire length and damages as a result of excesstensile forces are prevented. Such a method for blowing in a cable isdescribed in EP-A-0,292,037. A combination of blowing in and pulling isalso possible by attaching, at the end of the optical fibre cable, aso-called shuttle.

Under certain circumstances, it is undesirable to cut through theexisting cable in order to thus be capable of sliding the duct over it.Such is the case, e.g., if the cable must remain available for otherpurposes.

SUMMARY OF THE INVENTION

An object of the invention is to offer a solution for said problem.

According to a first aspect the invention therefore provides for amethod of the aforementioned type, a tape-shaped element around theexisting longitudinal element during propulsion being formed into a ductclosed all around, by coupling to one another coupling means present atthe longitudinal edges of the tape-shaped element.

According to a further object the invention provides for a tape-shapedelement provided, along the longitudinal edges, with coupling meanscarried out, according to a preferred embodiment, as complementaryclosing members. Said closing members are, e.g., of the “Zip-lock” type,comprising a closing member having an upright, barbed longitudinal edge,and a closing member having a longitudinal slot in the walls for whichopenings have been mounted for encasing the barbs. Other coupling orclosing systems, however, may also be applied, and are well-known tothose skilled in the art.

It should be noted that a tubular member having a closing member of thetype which is also applicable in the event of the tape-shaped elementaccording to the invention, is known per se as an insulation for heatingtubes. In this connection, the tube may be opened along a longitudinalcut to such an extent that it may be placed over the heating tube, andsubsequently may be closed by way of the closing members around thetube.

The invention is based, among other things, on the insight thatinterrupting an existing cable is not required, when the duct to beapplied around it is not initially closed all around, but is graduallyfolded around the cable from a tape shape during installation and, indoing so, is closed to the then opposite longitudinal edges of thetape-shaped element.

The existing cable may continue to be permanently in the ground and, inthis case, is enclosed by the duct, which may have the advantage that,e.g., a cable having a lead sheating continues to be insulated withrespect to the surrounding ground. It goes without saying that theexisting cable may also be removed from the duct at any desired moment.

The use of a tape-shaped element for forming a duct has the additionaladvantage that significantly less space is required for storage, thatthe transport is simpler, and that it does not have the tendency tocontinue to be curved, as a tube would, as a result of winding it arounda reel.

A further advantage is that a small bending radius is possible, as aresult of which installation in smaller spaces poses no problem.

According to a preferred embodiment, the tape-shaped element isprovided, over its length, with one or, preferably, several microducts.This offers numerous advantages. To start with, no separate microductsneed be applied afterwards in the installed duct. Secondly, themicroducts give the tape-shaped element additional rigidity in the eventof it being pushed down into the ground, and in the third place themicroducts, when they are located on the outside of the duct, may beinterrupted in a simple manner, and released from the ductcircumference. From such a microduct released from the duct, therequired welds for, e.g., connections to homes, may be made. It is alsopossible to provide both sides of the tape-shaped element withmicroducts or, if the microducts are located to one side only, to formthe closing members in such a manner that the tape-shaped element may beoptionally closed with the microducts on the inside or the outsidecircumference of the duct.

The tape-shaped element may be manufactured of synthetic substance,e.g., of HDPE—high-density polyethylene. The tape may consist of severallayers, if so desired, it being possible, e.g., to include an aluminiumlayer as water-retaining element.

Within the framework of the invention, it is also possible to implementthe tape-shaped elements in such a manner that these are capable ofbeing coupled in the transverse direction as well, by way of the closingmembers, as a result of which ducts having variable diameters may beformed by manufacturing them from one or several tape-shaped elementscoupled sideways.

A further variant of the invention is a tape-shaped element havingmicroducts, there already having been integrated preferably opticalfibres or cables into the microducts; particularly the so-calledplastic-optical-fibre (=POF) cable is suitable for this purpose.

According to a still further aspect the invention provides for a systemfor carrying out the method according to the invention, comprising meansfor supplying a tape-shaped element which is provided with longitudinaledges thereof which are capable of being mutually coupled, means forfolding around a longitudinal element of the tape-shaped element andcoupling to one another longitudinal edges, means for transporting, withrespect to the longitudinal element, a tape-shaped element formed into aduct, and means for feeding a fluid to the front end of the duct. If thetape-shaped element is provided with microducts, the latter may be usedfor giving off the fluid towards the front end of the duct in order tosufficiently loosen the ground around the existing longitudinal elementand/or to wash it away in order to make room for the duct.

BRIEF DESCRIPTION OF THE DRAWINGS

Below, the invention will be further clarified on the basis of exemplaryembodiments with reference to the drawing. In it,

FIG. 1 shows a schematic view of an arrangement which is suitable forimplementing the method according to the invention;

FIGS. 2 a and 2 b show views in perspective of a tape-shaped elementaccording to the invention;

FIG. 2 c shows variants of the closing members;

FIG. 3 shows a view in transverse section of a tape-shaped elementaccording to FIG. 2, formed into a duct according to the invention;

FIG. 4 shows a schematic view of a possible device for forming a ductout of a tape-shaped element;

FIG. 5 shows a schematic view of means for closing the tape-shapedelement into a duct, and propelling the duct formed in this manner.

In the figures, similar components are indicated by the same referencenumerals.

DETAILED DESCRIPTION

FIG. 1 shows a general schematic view of a device for carrying out themethod according to the invention. In general, for further detailsrelating to the present device, in so far as applicable, reference maybe made to the aforementioned U.S. Pat. No. 5,639,183.

The device comprises a reel 1 on which a tape-shaped element 2, whoseexemplary embodiment is shown in more detail in FIG. 2 a, 2 b and FIG.3, has been wound. A closing and conveyor device 3, which is shown inmore detail in FIG. 4, closes the tape-shaped element 2 into a duct 2′around an existing longitudinal element 4, such as a cable, located inthe soil. For simplicity's sake, below there will be spoken of a cable4, but it will be understood that the invention may also be applied withother longitudinal elements, such as, e.g., water or gas tubes. Thedevice 3 is provided with means 6 for anchoring the device with respectto the cable 4 and thus preventing the device from shifting with respectto the cable 4 instead of the duct 2′ around the cable. The device 3 isfurther provided with means of transport 7, 7′, such as conveyor rollersor belts, serving to form the tape-shaped element 2 around the cable 4into a duct 2′, and to propel said duct along the cable. At the frontend, the duct 2′ is provided with a spouting headpiece 5, which isprovided with openings through which a fluid under pressure may beconducted to loosen and/or widen the soil surrounding the headpiece 5 inorder to free the way for the duct 2′. The fluid is, e.g., water orbentonite, which is fed to the reel 1 by way of a line 8. In the eventof a tape-shaped element 2 which is provided with microducts to be dealtwith below, the fluid may be conducted to the headpiece 5 by way of saidmicroducts. If there are no microducts involved, the fluid is fed to thedevice 3 in order to be directly fed to the interior of the duct 2′.

FIG. 2 a shows the tape-shaped element 2 in more detail. Said elementconsists of a carrier 10 which may consist of synthetic substance, suchas HDPE, may consist of one and possibly of several layers having, e.g.,an intermediate aluminium layer as water-retaining structure. Thelongitudinal edges of the carrier 10 are provided with coupling means inthe form of closing members 11 and 12, which are complementary and maybe, e.g., of the type which is applied as “Zip-lock” in the event ofplastic bags. In this case, the closing member 11 consists of a body 13having an elongated ridge 14 provided with barbs not shown, and theclosing member 12 consists of a body 15 having an elongated slot 16 inwhich openings have been applied which are capable of co-operating withthe barbs.

FIG. 3 shows a tape-shaped carrier 2 in the status of having been formedinto a duct 2′, the closing members 11 and 12 engaging with one another.

Preferably, the carrier 10 is provided with one or more microducts 17which, either directly but preferably by way of a connecting ridge 18,are connected to the carrier 10. The advantage of applications of such aconnecting ridge 18 is that a microduct 17 may be simple to release fromthe tape-shaped element, e.g., by cutting into the ridge, as is shown inFIG. 2 b. Said releasing of a microduct from the duct 21 offers anadvantage in the event of forming branchings to, e.g., homes.

The microducts 17 may be applied either to one side of the tape-shapedelement 10 or on either side. If they are applied to one side, they mayoptionally come to lie along the internal circumference or the externalcircumference of the duct 2′.

The microducts 17 may be empty, so that an (optical) cable or fibre maybe applied therein, but may also be provided in advance with, e.g.,plastic optical fibre or other optical fibres or cables. The diameter ofthe microduct 17 is, e.g., 5–7 mm.

The carrier 10 is preferably provided with a longitudinal ridge 19 shownonly in FIGS. 3 and 5, which is applied at the location of any of themicroducts 17 and which, just as the closing members 11, 12, serves tobe engaged by the means of transport 7, 7′ to propell the duct 2′. Bycarrying out said propulsion on either side of the duct, a regulartransport takes place.

FIG. 2 c schematically shows variants of the closing members, whichfacilitate the optional closure of the tape-shaped element 2 in severalways, namely, having the microduct at the internal or external side, andto couple the tape-shaped element transversely in order to be capable ofthus manufacturing ducts having variable diameters. To this end, theclosing members 11 and 12 may be provided with two further elongatedridges 14′ and two corresponding elongated slots 16′ respectivelyparallel to and transversely oriented to a plane of carrier 10. It goeswithout saying that each of said options may be separately applied.

FIG. 4 shows, in more detail, the device 3 consisting of 2 pivotablyconnected parts 20, 20′ in order to be capable of placing the devicearound the cable 4. Moreover, the device is provided with an inputopening 21, by way of which the tape-shaped element 2 is conducted intothe device. The shape of the opening 21 may be adjusted to the width ofthe tape-shaped element 2 and to the number of microducts 17 present.

FIG. 5 shows a possible embodiment of means of transport 7, 7′ forclosing the closing members 11 and 12 of the tape-shaped element 2, andfor propelling the duct formed after closure. The means 7, 7′ and thepair of means of transport engaging with the ridge 19, not shown,located on the opposite side of the duct, each consist of a pair ofdrive wheels 22, 23 and a conveyor belt 24 running around it. It goeswithout saying that other closing means and means of transport arepossible, and that there is provided for a drive for the wheels 22, 23.It is also possible to apply closing means only and to have thetransport of the duct 2′ carried out along the cable 4 by the headpiece5. For this purpose, the headpiece 5 may be realised, e.g., as a drillbit. Other ways of propelling the duct, too, are imaginable, e.g., byway of mechanical tensile force, manual pushing or pulling force etc.Over shorter sections, the tape-shaped element may be pulled, e.g., withmanual force through the device 3 in order to form a duct around anexisting cable.

1. A method for installing a duct, a longitudinal element being presentalong a section over which the duct is to be installed, the longitudinalelement being utilized as a guide for the duct to be installed, themethod comprising the steps of: supplying a tape-shaped element; formingthe tape-shaped element around the existing, longitudinal element, thusforming a duct closed circumferentially around the longitudinal element,by coupling to one another closing members present at longitudinal edgesof the tape-shaped element; and propelling the duct over thelongitudinal element; wherein, to form a branch in the duct, thetape-shaped element has a carrier provided on at least one side thereof,with a number of microducts, one of the microducts being cut andreleased from the circumference of the duct.
 2. The method recited inclaim 1 wherein a fluid is fed through the duct to a front end of theduct.
 3. The method recited in claim 1 wherein a fluid is fed through atleast one of the microducts.